1. Field of the Invention
The present invention relates generally to the field of cutting shears, and more specifically, to cutting shears with a longitudinally slidable and preferably rotatable thumb ring that moves ergonomically with the thumb during use.
2. Description of the Related Art
There are a number of cutting shears incorporating longitudinally and/or rotationally adjustable thumb and finger rings that are the subject of issued patents or published patent applications, but none of these inventions includes the novel features of the present invention, most notable a thumb ring that is readily slidable back and forth in the longitudinal direction and readily pivotable for a comfortable thumb angle during use of the scissors, while in addition, the thumb ring is automatically restrained in its last position when the thumb is temporarily removed from the ring.
U.S. Pat. No. 1,479,908 (Goshia, 1924) discloses scissors with an automatically adjustable thumb ring that is connected to the shank of the scissors via a rivet pin fitted with a friction roller. The thumb ring is designed to slide forward and backward on the shank (i.e., the handle) with each opening and closing of the scissors. The thumb ring may be optionally locked in place with a set screw. There is no provision in this invention for automatic restraint of the ring when the thumb is removed from the ring.
U.S. Pat. No. 2,158,277 (Dolph, 1939) provides scissors with a manually adjustable thumb ring, which may be set to any one of a number of discreet positions along the shaft. The discreet positions are determined by a set of teeth along the shaft that mate with a set of matching teeth on the thumb ring.
U.S. Pat. No. 2,571,675 (Bray, 1951) describes scissors with removable thumb and finger rings, in which the thumb ring may be longitudinally adjusted and locked into position prior to use, and in which the diameters of the thumb and finger rings may be adjusted to fit hands of various sizes.
U.S. Pat. No. 4,642,895 (Gauvry, 1987) discloses scissors having a thumb loop that is rotatable longitudinally along and perpendicularly around the axis of the scissors handle by means of a ball and socket interconnection. The invention also comprises a rubber stop or bumper to limit the closing of the blades. In this invention, the thumb loop does not slide freely along the longitudinal axis of the handle; instead, it only rotates around the ball and socket joint.
U.S. Pat. No. 5,469,624 (Benton et al.) provides scissors and similar instruments that comprise interchangeable, rotatable and pivotable thumb and finger rings that incorporate a hand-adjustable tensioning means. The rings are not capable of sliding longitudinally along the handle.
U.S. Pat. No. 6,212,780 (Huang, 2001) describes scissors and similar instruments that comprise a thumb ring that may be adjusted longitudinally along the handle and set a discrete points prior to use, using a cam lock or screw as a locking means.
U.S. Pat. No. 6,249,977 (Knopp, 2001) discloses scissors having a T-shaped finger grip and a thumb ring grip, in which each of the two grips can be adjusted longitudinally along a handle and secured at the desired position with a locking screw.
U.S. Pat. No. 6,915,578 (Yusufov et al., 2005) and U.S. Patent Application Publ No. 2004/0211068 (Yusufov et al, 2004) provide a reversible-blade scissors comprising finger and thumb rings that are longitudinally and pivotable adjustable. Each ring is secured both longitudinally and pivotably by a single thumb screw prior to use of the scissors. The shafts of the thumbs screws are fitted into longitudinal slots, (i.e., tracks), in which the tracks are within flat sides of the handles, and the flat sides of the handles are in the same plane as the flat sides of the blades.
U.S. Pat. No. 7,424,778 (Benton, 2008) and U.S. Patent Application Pub. No. 2005/0204569 (Benton, 2005) describe scissors having a pivotable adjustable thumb ring, wherein the pivot shaft is made of flexible material, thereby allowing the ring to flex as well as pivot. There is no longitudinal adjustment of the thumb ring in this invention.
U.S. Pat. No. 7,966,733 (Jun, 2011) and U.S. Patent Application Pub. No. 2008/0172886 (Jun, 2008) disclose scissors comprising a thumb ring that is capable of rotating in two independent directions and pivoting around one axis that is parallel to the handle. The thumb ring of this invention is not capable of longitudinal adjustment.
U.S. Patent Application Pub. No. US 2006/0010695 (Wu, 2006) provides thumb and finger rings for scissors that are rotatable and detachable. There is no provision for longitudinal adjustment of the rings in this invention.
U.S. Patent Application Pub. No. US 2010/0192384 (Fox, 2010) describes shears having a pivotable and flexible finger ring. There is no provision for longitudinal adjustment of the ring in this invention.
U.S. Patent Application Pub. No. US 2010/0212165 (Parnazzina et al., 2010) discloses scissors with a pivotable thumb ring and saw-toothed edges on the blades. There is no provision for longitudinal thumb ring adjustment in this invention.
U.S. Patent Application Pub. No. US 2010/0242289 (Roskam et al., 2010) provides scissors comprising an articulated thumb ring that is magnetically attached to the handle. The thumb ring may be detached and reattached to the handle during use of the scissors without removing the ring from the thumb.
U.S. Patent Application Pub. No. US 2011/0016728 describes a scissors with thumb ring that is adjustable for offset, rotation, and diameter. There is no provision for longitudinal adjustment of the thumb ring in this invention.
U.S. Pat. No. D536,941 (Nenadich et al, 2007), D537,312 (Nenadich et al., 2007), and U.S. Design Pat. No. D538,612 (Nenadich et al, 2007) illustrate scissors having pivotable (but not longitudinally adjustable) thumb rings.